The invention relates to an apparatus on a spinning room machine, especially a spinning preparation machine, for example a flat card, roller card or the like, for monitoring an electric drive motor.
In practice, spinning room machines have rotating operating elements (for example cylinders or lickers-in in the case of a carding machine) which are driven by an electric motor. In order to be able to match their speeds to different operating conditions there are frequently used speed-setting or regulating devices, for example frequency converters. As a rule, the motors are so designed in respect of their output capacity that they correspond to the demands in question plus a certain reserve. Where demands vary in dependence upon the operating situation in question, the motors always need to be dimensioned for the highest possible demands. The same is also true of the speed-setting or regulating devices operating the motors. In operation, those devices are able to deliver significantly more power than would be necessary for the motor in question in normal operation. Such a case arises, for example, when a frequency converter is also employed for the electrical braking of the motor. In that case, the braking current delivered by the frequency converter and required for a serviceable result can easily be twice the nominal motor current. Because, in a normal case, there is no monitoring at all between the speed-setting or regulating devices and the motors, in the case of the arrangement described an increase in the power consumption of the motors, for example triggered by a defective bearing, sluggishness of the entire system or some other form of overloading, becomes apparent only when the maximum current limit of the speed-setting or regulating device is reached or exceeded. In such a case, however, it is generally already too late for the motor, especially because it usually involves overloading that begins slowly and persists over a long period. In most cases, the motor, or other drive elements associated therewith, has by that time already been permanently damaged or destroyed.